Application of refractory castables in coke oven

Application of refractory castables in coke oven

(1) Characteristics of refractory castables

Many properties of refractory castables depend to a considerable extent on the variety and quantity of binders, and the strength depends on the bonding strength of the binders. The fluidity of refractory castables is generally higher than that of ramming materials. Therefore, most castables are only poured or poured and then vibrated, so that the components in the mixture can be closely arranged and filled with the model.

After the refractory castables are formed, appropriate measures must be taken to promote hardening according to the hardening characteristics of the binder. For example, cement should be cured under appropriate humid conditions; some metal inorganic salts should be dried and baked.

The high temperature properties of refractory castables are also closely related to the variety and dosage of binders. If the selected granular and powdery materials have good refractoriness, and the melting point of the binder is high and will not react with the refractory material to form a low melt, the castable must have quite high refractoriness. If the material of the granular and powdery materials used is certain, the refractoriness of the castable is controlled by the binder to a considerable extent. Since in the refractory castables prepared with general aluminate cement, the fusible components are contained in the cement stone, so the amount of cement has a very significant effect on the high temperature properties of the castable.

When cement is used as a binder, in the process of high temperature use, the cement stone can be decomposed and dehydrated, and other phase changes and sintering occur, so that the castable changes in volume and also changes in structure. Since the change of the phase in the cement stone varies with temperature, the furnace lining made of this castable forms different components and structures at different distances from the working surface. Between various layers, internal stress or even cracks may occur due to the change of specific volume. In the sintering zone, because the granular material has been pre-fired, it only expands with the temperature rise, while the cement stone shrinks a lot, and the difference between the two deformations increases, so that the cement stone and between the cement stone and the granular material are combined. It has suffered considerable damage and is prone to cracks. Not only local cracks may occur at the interface between the two, but even sheet-like cracks perpendicular to the working face may occur. When the temperature fluctuates, the stress due to the difference in thermal expansion rate can cause the lining to peel off along this crack. This kind of situation that the structure is loose due to the decomposition and dehydration of the cement stone and easy to peel off due to the formation of a layered structure is often one of the main factors for the damage of the castable made of cement.

(2) Application of castables

Castable is currently the most widely produced and used monolithic refractory material. It is used to construct various heating furnace linings and other integral structures. For example, phosphate castables can be used in coke ovens.